On simulating shoreline evolution using a hybrid 2D/one-line model

Hybrid 2D/one-line shoreline models are becoming increasingly applied over the mesoscale (10 1 –10 2 years; 10 km) to inform coastal management. These typically apply one-line theory simulate changes in morphology based on littoral drift gradients calculated from a 2DH coupled wave, flow, and sediment transport model. However, key boundary conditions needed effectively hybrid their applicability beyond simple planform morphologies uncertain, which can potentially comprise management decisions. To address these uncertainties, an extensive numerical modelling campaign is carried out both assess sensitivity calibrate advanced model (MIKE21) against six variables three different sandy system morphologies: (a) with gentle sloping profile, (b) steep (c) complex morphology. The considered include nearshore discretisation, bathymetry, bed friction, sand grain diameter, porosity, grading, weir coefficient of hard defence structures. Five conclusions derived testing calibration results. First , optimal for evolution vary according geomorphology processes. Second specifying within physically realistic ranges does not guarantee reliable predictions. Third discretisation should be treated as typical parameter finest most accurate predictions, defining process length scales also Fourth valid application plausibly because assumption spatially invariable closure depth. Fifth have limited where active beach profile subject direct human modification, due constant time-averaged form. findings provide theoretical insights into drivers systems, practical implications refining continued models. • approach tested morphologies. Optimal correspond observed parameter.